Audio technologies and compression algorithms, such as MP3 encoding and various streaming audio formats, have made it possible to deliver high quality audio over the Internet. MP3s are considered one of the more popular searches. MIDI (Musical Instrument Digital Interface) is less common. However, much of the music heard every day is written with and played by MIDI sequencers.
Many audio files found on the Internet are not free. Before using, please read the website for usage/rights information. If no such information is available it is advisable to seek usage permission by contacting the person who created the file.
According to copyright law, distributing or obtaining a copyrighted work (such as a music file) without the permission of the copy right holder is against the law.
It is illegal to download music files which are copyrighted. The same thing applies for burning compact discs of music that you have not purchased. It is also illegal, and you could face prosecution.
It is legal to download copyrighted songs if they have been made available by the artist for free download. To stay within the realm of legal, you must abide by their usage restrictions on the music. One can freely download non-copyrighted songs as well as copyrighted which you "own".
Searching for multimedia (audio):
There are several popular file formats for music. Singingfish.com or Alta Vista Audio Search will help you find many of them. Music in the the MIDI format can be found using the Ithaki search engine. You may need to download a special player for some of the file formats.
Ringbits.com is a ringtone search engine. It will search only through ringtone related websites to narrow down your search.
Findsounds.com is an award-winning free tool that will lead you to many types of sound files. Type in a few terms that describe the sound and press "Search"